Mark null and undefined as undetectable, and use it to handle abstract equality comparison in the g…

src/crankshaft/mips/lithium-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.7
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5234 matching lines @@
 
   } else if (String::Equals(type_name, factory->boolean_string())) {
     __ LoadRoot(at, Heap::kTrueValueRootIndex);
     __ Branch(USE_DELAY_SLOT, true_label, eq, at, Operand(input));
     __ LoadRoot(at, Heap::kFalseValueRootIndex);
     *cmp1 = at;
     *cmp2 = Operand(input);
     final_branch_condition = eq;
 
   } else if (String::Equals(type_name, factory->undefined_string())) {
-    __ LoadRoot(at, Heap::kUndefinedValueRootIndex);
-    __ Branch(USE_DELAY_SLOT, true_label, eq, at, Operand(input));
+    __ LoadRoot(at, Heap::kNullValueRootIndex);
+    __ Branch(USE_DELAY_SLOT, false_label, eq, at, Operand(input));
     // The first instruction of JumpIfSmi is an And - it is safe in the delay
     // slot.
     __ JumpIfSmi(input, false_label);
     // Check for undetectable objects => true.
     __ lw(input, FieldMemOperand(input, HeapObject::kMapOffset));
     __ lbu(at, FieldMemOperand(input, Map::kBitFieldOffset));
     __ And(at, at, 1 << Map::kIsUndetectable);
     *cmp1 = at;
     *cmp2 = Operand(zero_reg);
     final_branch_condition = ne;
@@ skipping 305 matching lines @@
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kPushBlockContext, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8